non-canonical GAT domain found in fungal class E vacuolar protein-sorting machinery protein Hse1 and similar proteins
Hse1 is a component of the ESCRT-0 complex which is the sorting receptor for ubiquitinated cargo proteins at the multivesicular body (MVB), and recruits ESCRT-I to the MVB outer membrane. Members of this family contain a non-canonical GAT (GGA and Tom1) domain consisting of two helices. A canonical GAT domain is a monomeric three-helix bundle that bind to ubiquitin. Hse1, together with another GAT domain-containing protein Vps27, forms a Vps27/Hse1 core complex that consists of two intertwined non-canonical GAT domains, each consisting of two helices from one subunit, and one from the other subunit. The two GAT domains are connected by a two-stranded coiled-coil. The Vps27/Hse1 complex, an intertwined GAT heterodimer, is a scaffold for binding of ubiquitinated cargo proteins and coordinating ubiquitination and deubiquitination reactions that regulate sorting.